I've never used it for wet applications, so I can't say with any confidence that it is waterproof. It has worked very well for me in the past to glue foam blocks together, and to glue skins onto the foam core of model airplanes. I have a pad made from thre 1" layers of minicell type foam (a backpacking sleeping pad) that I use as a cushion under a child carseat to protect the upholstery. It has alot of pressure on it, and has done okay. I would probably put a bead of silicone sealer around the edges and clmap between to pieces of plywood (or lay on floor and weight a plywood pad a little larger than the foam)

Small scale experiments are a good way to test this sort of thing. Post the results here so we can learn from your efforts. By exchanging info we can all save each other some work, and greatly increase our knowledge.

I have also considered using a skim coat of silicone instead of spray glue, but I don't know if it will attack the foam.

> Aha, so is Scotch 77 the magic number? Mark?